ICND 2 Flashcard: Frame Relay

Frame Relay allows the expansion of the WAN with less hardware by providing virtual circuits; less costly than running multiple leased lines like HDLC and PPP.

For example Router 1 (DTE) at your company site has to connect to Router 2 (DTE) at the other site. In between is the Frame Relay cloud. The Router 1 connects to one switch (DCE) in the cloud, and the other Router 2 connects to anothr swtich (DCE). Router 1 could also connect to a Router 3 and so on.

One router is an access linl which can support multiple virtual circuits to send data to multiple remote routers. Each link is a virtual circuit. The data link header and trailers on each frame. The header holds ad address filed called a DLCI.
DLCI - Data Link Connection Identifier

The notes for this section are taken from the first CCNA Bootcamp course I studied in 2003 by Marketbridge Technologies in Hull-Gatineau. http://www.marketbridge.com/#  The company has grown and changed alot over the years from offering courses to consulting services, but the owner remains the same so it's probably the same company.

Two Frame Relay encapsulations: Cisco and IETF
Cisco is the default, and it means that you have a Cisco router on each end of the Frame Relay network. If you don’t have a Cisco router on the remote end of your Frame Relay network, then you need IETF encapsulation.

Frame Relay is a cost efficicient technology, for intermittent connection from LAN or between endpoints to major backbones or a public WAN.  A permanent virtual circuit (PVC) is formed, enabling the customer to perceive a continous, dedicated connection without having to pay for a full-time leased line; the ISP determines the route each frame travels to its destination and can charge based on usage.  Think of it as shared bandwidth, a portion of the dedicated paid bandwidth to allotted to each user; allows the user to exceed the guaranteed bandwidth if resources are available

However for a truly private network, Frame Relay would run over leased lines over T-1 lines. A dedicated connection during the transmission period is required, but without a steady flow of transmisions, so it is not often used for voice or video.  The data units are in frames in variable sizes.

Packet based switching.
Frame relay is based on the older X.25 packet-switching technology which was designed for analog voice. Frame relay today is fast packet switching because it operates in the Layer 2 data-link layer and not so much Layer 3 network even though a frame can carry packets of Ethernet and X.25 Error checking or resending is up to to the endpoints to evaluate.

DLCI - Data Link Connection Identifier

I really like the description of a frame-relay map and how it joins an DLCI with an IP address much like ARP mapping MAC address to IP. See the IP-to-DLCI mappings with the command, show frame-relay map (IARP is default on Cisco routers).

Possible network topologies
Hub and Spoke: one hub many spokes used with sub interfaces
Partial Mesh or Hub and Spoke - routers do not have a VC to all other routers

Full Mesh: each router has a logical circuit to every other router

Hybrid: Two remote routers may have VC to each other providing full mesh connectivity between them and the hub. The other remote routers may have only one VC back to the hub.
Frame-Relay LMI
Frame-Relay used the Local Management Interface (LMI) protocol to generate keepalives and obtain a status on the virtual circuits.  LMI message formats: Cisco (DLCI 1023), ANSI or Annex D (DLCI 0), and Q.933A or Annex A (DLCI 0?) containing info regarding -

• Keepalives
• Multicasting - Multicasting uses the reserved DLCIs from 1019 through 1022.
• Global addressing - This provides global significance to DLCIs, like a LAN
• Status of virtual circuits - This provides DLCI status.

Possible states for the circuits
Active - the circuit is up and running
Inactive - possible cause, circuit to CO (frame switch) is find but remote end is down
Deleted - circuit to CO not working, interface down or cabling issue, no LMI

Congestion Control in Frame-Relay
DE - Discard Eligibility, mark for packets exceeding the CIR
BECN - Backward Explicit Congestion Notification, tell source to slow down transmission
FECN - Forward Explicit Congestion Notification, tell destination there was congestion in the cloud
An excellent summary of everything you need to know about Frame Relay for Cisco CCNA, written like a study blog with network diagrams. The style of writing is like an instructor speaking. Click here.

usage: conf t
encapsulation frame-relay

Scenario
There are seven remote sites to connect and only one serial port on the router. Instead of seven leased lines, frame-relay might be a good soluction to statistically multiplex multiple logical circuits over one physical interface to save money.

Access rate The maximum speed that the Frame Relay serial interface can transmit.

CIR The maximum bandwidth of data guaranteed to be delivered. In reality, it’s the average amount that the service provider will allow you to transmit.

For example if the T1 is carrying an access rate of T1 (1.544Mbps) and you're paying for a CIR of 256Kbps. The first 256Kbps of traffic you send is guaranteed delivery. Beyond that, it's a “burst”— a transmission that exceeds the guaranteed 256Kbps rate and up to the T1 access rate (if that amount is in your contract). I believe this sounds like the whole discussion about paying for bandwidth usage and doing away with unlimited with the CRTC ruling??

Obviously if the combined committed burst (the CIR) and excess burst sizes, known as the MBR or maximum burst rate when combined, exceed the access rate, then the packets will be dropped, depending on the service provider.

ICND2 Flashcard: EIGRP

EIGRP = Enhanced Interior Gateway Routing Protocol

It is a Cisco proprietary, Advanced Distance Vector metric. Some folks may refer to it as a hybrid routing protocol, but it is truly not.  EIGRP uses Hello packets, much like a link state protocol

Advertised distance - EIGRP metric for blank to reach network
Feasible distance - the metric to reach neighbor + the advertised distance

Features of EIGRP
Rapid convergence using Diffuse Update Algorithm (DUAL) guarantees loop free paths and backup paths.  If the primary route in the table fails, the best backup route is added to the table immediately. If no route exists, EIGRP queries the neighbors.

Reduced bandwidth by not sending the entire database and instead using:
Partial updates: only include route changes, incremental updates and not the whole table
Bounded updates: only send updates to routers affected

Multiple Network Layer Support can do Appletalk, IP, IPv6, Novell (IPX)

Less Overhead by using multicast and unicast, not broadcast. The ip address 224.0.0.10 is listed in my notes

Classless Routing
The mask is advertised for each network as this provides smaller subnets and efficient use of IP addresses.  The protocol can also support discontiguous subnets and VLSM (variable length subnet masks)

Load Balance
The protocol allows load balancing on equal (by default) and unequal cost paths. Caveat, for unequal cost paths, variance must be specified.

EIGRP does equal metric load balancing by default up to four equal metric routes. This means the variance value is 1 (default).  The routing table can have 16 entries for the same destination.

Configuring EIGRP
usage: conf t
router eigrp 100 (automonous system 100, 1 to 65535 possible)
network 10.0.0.0
network 192.168.10.0 0.0.0.15 (the wildcard mask can advertise subnets now)
no auto-summary (what does this do?)
variance 2

Verifiy EIGRP
show ip route eigrp
show ip protocols
show ip eigrp interfaces
show ip eigrp int fa 0/0
show ip eigrp int 100
show ip eigrp topology
show ip eigrp topology all-links
show ip eigrp traffic (this command lists number of packets sent/ received; HELLO, updates, queries, replies, ack etc)

More about the Variance Command
This command allows unequal metric load balancing, metrics being
* bandwidth
* delay
* reliability - the most reliable based on keepalives
* load
* K value - calculation method and AS number must match

Troubleshoot EIGRP
show ip eigrp neighbors
show ip int brief (shows which interfaces are active)
show ip int fa 0/0 (see ip subnets)
show ip protocols (see routing for networks)
show ip eigrp int (check for the process id and the same K method)
debug eigrp packets

show ip route (displays all the routes and eigrp is labeled)
show ip eigrp topology (shows the router id with the highest IP address which should be the loopback 0)

Who are your online friends?

Ego-surfing

So I did a google search on myself because my colleagues claimed that they searched everywhere on the Internet for me, to find my phone number, but they could not find me. I'm not convinced because I am who I am. I run the search myself on my firstname lastname city; most hits on the first page are true, albeit outdated.  A job I posted as a prospective employer, an old work email address that got too much spam, what I studied and where I went to school, my volunteer work at a professional organization, and my resume as a piano teacher resume. The part about me running a half marathon? That's not true. LOL  I am registered for a mini-triathlon, but no I have never run that far in my life.

On the next page I see a Linked In profile for a girl with the same name as mine in Washington. She's American but not asian, with 30 years of experience in Law Enforcement, industry specific skills and two big stints in Interpol. Her photo is a really good looking chic, probably age 25. I'm nice so I decide to send her a friendly note to say... "hey we have the same name but your resume is so amazing! But the linked in profile is wide open to the public and you have security clearances, perhaps you could change the default privacy settings, but you don't have to friend me." I had to send the message like a "connection request" because that's the only way you can contact someone you are not actually connected to.  Surprisingly, she accepts. I'm intrigued by this mysterious and successful persona with my name.  I get frequent updates that she has new connections joining her from Northrop Grumman (US DOD contractor) and other interesting people.  In the back of my mind, I have suspicions why someone has 30 years experience and looks 25 (but that cannot be a crime).


Managing your online relationships

I decide to talk to my old boss because he is in the IT Security industry, he would know what to say about these kind of sticky things I get myself into. He jokes that women with my name simply cannot be trusted. He sends me a link to this article about the famous Robin Sage Experiment. It's a good read about basic online security awareness and social engineering.  The "girl" who duped military intelligence and top notch IT Security professionals.

He reassures me that he did some peripheral background checks on my new contact and the info in her resume does check out; and he even convinces me that based on her info if she is 46, well some women could still look that good. (So that confirms that he thinks she is good looking too) But he cautions me with something I should know already, as a general rule, be careful about being friends with someone you haven't actually met in real life.

Another time on Facebook, I accepted a friend request from a person who I assumed was a twenty-something year old friend of my sister because it was a name I thought I recognized.  As soon as I accepted, she chatted me up and started her note with "hihi" and her writing style was very girly and teeny boppy and we talk about similarities with her hometown Vancouver and mine.  Her friend list is full of really good looking asian chics, but no guyz. Well that's odd but I think nothing of it.  Over the course of weeks we continue to talk, about Victoria Day long weekend, how cute the kids are with tulips. Soon after I get a friend request from her again because she told me her account got locked so she started a new one. This keeps happening on a weekly basis and I decide to forget about it. On a whim I search for her profile name and there are many many profiles (without a profile picture) with her name, but there was one with a photo of a really ugly looking guy. Reminds me of a guy who did too much boxing in the face, was my first impression. I was shocked to learn that my new "friend" was probably some kind of predator. What should've been my first clue? What kind of teeny-boppy girl doesn't have guy friends on the friend's list?


Managing your online profile

You ask yourself, Who am I? Well if you feel the need to do some ego-surfing and google yourself and if you don't like what you see, here is a good article I found about un-googling yourself and managing your online identity a little bit better. Un-google yourself!

Verify the privacy settings on your various social media websites, especially access policies to the photos you post of yourself and your own children! Google has recently updated their privacy policy, which makes it harder to delete your online search history. So, um don't google something criminal like that other guy, "where to hide a body".

ICND 2 Flashcard: Routing OSPF

This material on link-state routing protocols is supposed to be ICND2 but I'm just gonna say that you should still study this for ICND1 because I said so, and wish I did. Hello!

OSPF Configuration Commands

usage: conf t
router ospf 100 (numbers 1 to 65535 valid)
log-adjacency-changes
network ipaddressofnetwork wildcardmask area number
network 10.1.1.0 0.0.0.255 area 0

router-id
Create a router's interface loopback 0 address first
Turn on OSPF
If the IP address ever changes, use the command, clear ip ospf proces

1) This part can be configured here, else
2) Choose the highest of loopback interfaces, else
3) Choose the highest of active interfaces

Verification of OSPF working
show ip route (shows all the routes the router knows and how they are learned, O = OSPF)
show ip protocols
show ip ospf (displays general information)
show ip ospf interface (area id, adjacency info)
show ip ospf neighbor ipaddress mask

The command, show ip route, is very useful because it also shows the interface of the learned routes. I had a scenario to set up two encrypted tunnels for redundancy. I did a show ip route from router2 and I noticed that all the networks I was looking and learned from OSPF were listed; I was quite perplexed that the routes were not learned from the secondary tunnel associated with router2. Everyone thought I was quite the wizard to get all the systems green again, high fives all around, and no one really cared to listen what I was still concerned about.

Eventually I figured out that the routes were obviously learned by OSPF through the interface to router1 whose tunnel is indeed up, which verifies OSPF learned routes to distant networks works but my intended secondary tunnel was not up. I did some digging and discovered I was missing the tunnel's source ip address in the interface tunnel configuration, what a silly rookie typo. But that's proof that OSPF was working so well I had fooled everyone (but not myself).

Logically, a hub and spoke topology or partial mesh? You be the judge.
Authentication of OSPF
service password-encryption (otherwise the key will be in plaintext)
ip ospf authentication-key plainpas
ip ospf authentication OR
area 0 authentication (you can choose md5)

Troubleshooting OSPF
Consider possible errors in neighbor adjacency's, routing table, and authentication.
The authentication methods are 0 = null, 1 = simple pssword, 2 = md5

OSPF means Open Standard Shortest Path First
- It is Classless IGP within a larger AS operating as a single OSPF network on Cisco
- A Link State protocol propagates the LSA's and not routing table updates

These are flood to all OSPF interfaces in the area
- the description of the interface
- advertises immediately state changes
- periodic update of entire database in 30 minutes
- forms a link state database
- calculates the shortest path using a SPF algorithm
- all routers in the area will have the same topological database; knowledge of distant routers

HELLO Protocol
- OSPF sends hello packets on an interface and confirms to OSPF routers the presence of another OSPF on the link, with each other
- bidirectional response
- adjacency is formed when two routers agree on area-id, hello/dead interval, authentication, stub, area flags

To reduce traffic there is one router chosen as the DR (designated router), a BDR (backup designated router) and the rest are DROTHERS.  The multicast ip address is used 224.0.0.5 and the router id used is the loopback interface.

COST
To calculate the cost of the link, use the reference bandwidth/ interface bandwidth in bits per second. For link speed greater than 100 Mbps use the ospf auto-cost reference-bandwidth.

http://ccie11440.blogspot.com/2007/11/why-are-some-ospf-routes-in-database.html